Cache memory is typically random access memory (RAM) that a computer processor can access more quickly than regular RAM. For example, recently accessed data and/or frequently accessed data may be stored in the cache. As the processor processes data and needs data from the regular larger RAM, it looks first in the cache memory to determine if the data is in the cache. If it is in the cache, the processor does not need to do a more time consuming read operation to access data from the larger memory. In a similar manner, cache memory may also be used to provide faster access to data stored on a mass storage device (or bulk storage device) such as a disk drive, an optical drive, a tape drive, etc. For example, it has been suggested to augment disk drives with flash memory as part of a non-volatile (NV) cache solution in a manner such that the cache (for example, non-volatile flash memory) would be included with the disk drive itself.
It is believed that a better solution than providing a cache as part of the mass storage device (for example, a hard disk drive) is to provide a non-volatile (NV) cache memory using platform-based technology. One example of a platform-based cache solution is to provide a cache that is not a part of the mass storage device but is included on the host platform. Consolidating the cache in the platform (for example, instead of having lots of smaller caches on each storage device) allows the one consolidated cache to provide service to all of the storage devices. Further, by being more closely integrated with the platform, the non-volatile storage cache also can be used more readily for other platform services (for example, shared with the BIOS, etc). One argument that has previously been raised as to why such a platform-based solution is not an attractive alternative is because the non-volatile cache can become separated from the mass storage device (for example, a disk drive). This separation between the cache and the storage device is referred to as cache disassociation. For example, the storage device may be transferred from one platform to another platform and then back to the original platform, or the storage device might be accessed by a different Operating System (OS) (for example, Linux) on a platform and then accessed by the first Operating System (OS) (for example, Windows) again. In such a scenario, there is a potential, for example, for disk drive corruption and/or incoherent cache contents when the disassociation and/or re-association occurs between the storage device and the platform.
One previous solution for cache disassociation detection is for the contents of the disk drive to be scrambled in such a way that if the drive were moved to a different system (platform) it would not function without special tools to unscramble the contents. Disassociation was detected when the drive contents were not scrambled as expected. However, this type of solution creates new encumbrances and requires special tools for handling typical Information Technology (IT) service methods. For example, when a laptop fails, an IT technician may want to transfer the hard drive to a new loaner laptop while the original laptop is serviced. The additional new tools and methods required by the previous solution described above make such a transfer a much more cumbersome process. Therefore, a need has arisen for detecting whether cache disassociation has occurred in a manner which eliminates this type of cumbersome requirements and is equally reliable in detecting disassociation. If cache disassociation were detected then steps could be taken to properly restore cache coherency.